Various types of machines may use a work implement to transfer material from a work site and load the material onto transport vehicles (e.g., dump trucks, railroad cars and the like). These machines include excavators, wheel loaders, backhoes and other material moving machines. The transport vehicles loaded by the machines may have a particular load capacity determined by a manufacturer's maximum load rating and/or other factors, such as, for example, weight restrictions for on-highway vehicles. To promote maximum utilization of the transport vehicles, it may be desirable to load each transport vehicle as close as possible to its load capacity. Overloading the transport vehicle, however, may have negative consequences. Particularly, placing too much weight on a transport vehicle can significantly increase maintenance costs for the transport vehicle or create costly delays if the excess material is removed prior to transport. Under loading the transport vehicle may also be undesirable if it creates inefficiencies due to added delays and expense required to make additional trips of the transport vehicles to move material around and to remove the material from the work site.
To monitor the weight of the material placed onto each transport vehicle, machine manufacturers have developed payload calculation systems. A payload calculation system may determine the weight of a material currently carried by the work implement (e.g., weight of material in an excavator bucket), as well as the total weight of a material loaded onto a transport vehicle during a particular cycle or time period. For improved productivity, the payload calculation system may determine the weight of a material carried by the machine and/or work implement while the machine and/or work implement is in motion rather than performing static measurements where static friction and other forces may influence the accuracy of the weight measurement.
One method for determining the weight of material in a work implement is disclosed in U.S. Pat. Appl. Publ. No. 2008/0169131 by Takeda et al. published on Jul. 17, 2008, entitled “Device and Method for Measuring Load Weight on Working Machine.” The Takeda et al. publication discloses a method for measuring the weight of a load accurately in a working machine for moving a load of material such as a wheel loader. While the load of material is lifted by a boom of the working machine, a boom angle and a pressure value of a boom cylinder are measured and a boom angular speed is calculated. A corrected factor is determined according to the boom angular speed, and a corrected pressure value is calculated based on the measure pressure value, the boom angular speed and the corrected factor. A predetermined table is referred to and the weight of the load is determined based on the boom angle and the corrected pressure value of the boom cylinder.
Although the corrected factor of the Takeda et al. publication may compensate for frictional effects of the movement of the boom of the working machine, other factors may exist that affect the accuracy of determining the weight of a load of material.